Immunoregulation of follicular renewal, selection, POF, and menopause in vivo, vs. neo-oogenesis in vitro, POF and ovarian infertility treatment, and a clinical trial

Ovarian microenvironment: challenges and opportunities in protecting against chemotherapy-associated ovarian damage

BACKGROUND

Chemotherapy-associated ovarian damage (CAOD) is one of the most feared short- and long-term side effects of anticancer treatment in premenopausal women. Accumulating detailed data show that different chemotherapy regimens can lead to disturbance of ovarian hormone levels, reduced or lost fertility, and an increased risk of early menopause. Previous studies have often focused on the direct effects of chemotherapeutic drugs on ovarian follicles, such as direct DNA damage-mediated apoptotic death and primordial follicle burnout. Emerging evidence has revealed an imbalance in the ovarian microenvironment during chemotherapy. The ovarian microenvironment provides nutritional support and transportation of signals that stimulate the growth and development of follicles, ovulation, and corpus luteum formation. The close interaction between the ovarian microenvironment and follicles can determine ovarian function. Therefore, designing novel and precise strategies to manipulate the ovarian microenvironment may be a new strategy to protect ovarian function during chemotherapy.

OBJECTIVE AND RATIONALE

This review details the changes that occur in the ovarian microenvironment during chemotherapy and emphasizes the importance of developing new therapeutics that protect ovarian function by targeting the ovarian microenvironment during chemotherapy.

SEARCH METHODS

A comprehensive review of the literature was performed by searching PubMed up to April 2024. Search terms included 'ovarian microenvironment' (ovarian extracellular matrix, ovarian stromal cells, ovarian interstitial, ovarian blood vessels, ovarian lymphatic vessels, ovarian macrophages, ovarian lymphocytes, ovarian immune cytokines, ovarian oxidative stress, ovarian reactive oxygen species, ovarian senescence cells, ovarian senescence-associated secretory phenotypes, ovarian oogonial stem cells, ovarian stem cells), terms related to ovarian function (reproductive health, fertility, infertility, fecundity, ovarian reserve, ovarian function, menopause, decreased ovarian reserve, premature ovarian insufficiency/failure), and terms related to chemotherapy (cyclophosphamide, lfosfamide, chlormethine, chlorambucil, busulfan, melphalan, procarbazine, cisplatin, doxorubicin, carboplatin, taxane, paclitaxel, docetaxel, 5-fluorouraci, vincristine, methotrexate, dactinomycin, bleomycin, mercaptopurine).

OUTCOMES

The ovarian microenvironment shows great changes during chemotherapy, inducing extracellular matrix deposition and stromal fibrosis, angiogenesis disorders, immune microenvironment disturbance, oxidative stress imbalances, ovarian stem cell exhaustion, and cell senescence, thereby lowering the quantity and quality of ovarian follicles. Several methods targeting the ovarian microenvironment have been adopted to prevent and treat CAOD, such as stem cell therapy and the use of free radical scavengers, senolytherapies, immunomodulators, and proangiogenic factors.

WIDER IMPLICATIONS

Ovarian function is determined by its 'seeds' (follicles) and 'soil' (ovarian microenvironment). The ovarian microenvironment has been reported to play a vital role in CAOD and targeting the ovarian microenvironment may present potential therapeutic approaches for CAOD. However, the relation between the ovarian microenvironment, its regulatory networks, and CAOD needs to be further studied. A better understanding of these issues could be helpful in explaining the pathogenesis of CAOD and creating innovative strategies for counteracting the effects exerted on ovarian function. Our aim is that this narrative review of CAOD will stimulate more research in this important field.

REGISTRATION NUMBER

Not applicable.

Which side of the coin are you on regarding possible postnatal oogenesis?

It is well known that oocytes are produced during fetal development and that the total number of primary follicles is determined at birth. In humans, there is a constant loss of follicles after birth until about two years of age. The number of follicles is preserved until the resumption of meiosis at puberty and there is no renewal of the oocytes; this dogma was maintained in the last century because there were no suitable techniques to detect and obtain stem cells. However, following stem cell markers, several scientists have detected them in developing and adult human ovarian tissues, especially in the ovarian surface epithelial cells. Furthermore, many authors using different methodological strategies have indicated this possibility. This evidence has led many scientists to explore this hypothesis; there is no definitive consensus to accept this idea. Interestingly, oocyte retrieval from mature ovaries and other tissue sources of stem cells has contributed to the development of strategies for the retrieval of mature oocytes, useful for assisted reproductive technology. Here, we review the evidence and controversies on oocyte neooogenesis in adult women; in addition, we agree with the idea that this process may occur in adulthood and that its alteration may be related to various pathologies in women, such as polycystic ovary syndrome, premature ovarian insufficiency, diminished ovarian reserve and several infertility and genetic disorders.

Generation of Tailored Extracellular Matrix Hydrogels for the Study of In Vitro Folliculogenesis in Response to Matrisome-Dependent Biochemical Cues

While ovarian tissue cryopreservation (OTC) is an important fertility preservation option, it has its limitations. Improving OTC and ovarian tissue transplantation (OTT) must include extending the function of reimplanted tissue by reducing the extensive activation of primordial follicles (PMFs) and eliminating the risk of reimplanting malignant cells. To develop a more effective OTT, we must understand the effects of the ovarian microenvironment on folliculogenesis. Here, we describe a method for producing decellularized extracellular matrix (dECM) hydrogels that reflect the protein composition of the ovary. These ovarian dECM hydrogels were engineered to assess the effects of ECM on in vitro follicle growth, and we developed a novel method for selectively removing proteins of interest from dECM hydrogels. Finally, we validated the depletion of these proteins and successfully cultured murine follicles encapsulated in the compartment-specific ovarian dECM hydrogels and these same hydrogels depleted of EMILIN1. These are the first, optically clear, tailored tissue-specific hydrogels that support follicle survival and growth comparable to the "gold standard" alginate hydrogels. Furthermore, depleted hydrogels can serve as a novel tool for many tissue types to evaluate the impact of specific ECM proteins on cellular and molecular behavior.

Deciphering reproductive aging in women using a NOD/SCID mouse model for distinct physiological ovarian phenotypes

Female fertility is negatively correlated with age, with noticeable declines in oocyte quantity and quality until menopause. To understand this physiological process and evaluate human approaches for treating age-related infertility, preclinical studies in appropriate animal models are needed. Thus, we aimed to characterize an immunodeficient physiological aging mouse model displaying ovarian characteristics of different stages during women's reproductive life. NOD/SCID mice of different ages (8-, 28-, and 36-40-week-old) were employed to mimic ovarian phenotypes of young, Advanced Maternal Age (AMA), and old women (~18-20-, ~36-38-, and >45-years-old, respectively). Mice were stimulated, mated, and sacrificed to recover oocytes and embryos. Then, ovarian reserve, follicular growth, ovarian stroma, mitochondrial dysfunction, and proteomic profiles were assessed. Age-matched C57BL/6 mice were employed to cross-validate the reproductive outcomes. The quantity and quality of oocytes were decreased in AMA and Old mice. These age-related effects associated spindle and chromosome abnormalities, along with decreased developmental competence to blastocyst stage. Old mice had less follicles, impaired follicle activation and growth, an ovarian stroma inconducive to growth, and increased mitochondrial dysfunctions. Proteomic analysis corroborated these histological findings. Based on that, NOD/SCID mice can be used to model different ovarian aging phenotypes and potentially test human anti-aging treatments.

Chito-oligosaccharides and macrophages have synergistic effects on improving ovarian stem cells function by regulating inflammatory factors

BACKGROUND

Chronic low-grade inflammation and ovarian germline stem cells (OGSCs) aging are important reasons for the decline of ovarian reserve function, resulting in ovarian aging and infertility. Regulation of chronic inflammation is expected to promote the proliferation and differentiation of OGSCs, which will become a key means for maintaining and remodeling ovarian function. Our previous study demonstrated that Chitosan Oligosaccharides (Cos) promoted the OGSCs proliferation and remodelled the ovarian function through improving the secretion of immune related factors,but the mechanism remains unclear, and the role of macrophages, the important source of various inflammatory mediators in the ovary needs to be further studied. In this study, we used the method of macrophages and OGSCs co-culture to observe the effect and mechanism of Cos on OGSCs, and explore what contribution macrophages give during this process. Our finding provides new drug treatment options and methods for the prevention and treatment of premature ovarian failure and infertility.

METHODS

We used the method of macrophages and OGSCs co-culture to observe the effect and mechanism of Cos on OGSCs, and explore the important contribution of macrophages in it. The immunohistochemical staining was used to locate the OGSCs in the mouse ovary. Immunofluorescent staining, RT-qPCR and ALP staining were used to identify the OGSCs. CCK-8 and western blot were used to evaluate the OGSCs proliferation. β-galactosidase(SA-β-Gal) staining and western blot were used to detect the changing of cyclin-dependent kinase inhibitor 1A(P21), P53, Recombinant Sirtuin 1(SIRT1) and Recombinant Sirtuin 3(SIRT3). The levels of immune factors IL-2, IL-10, TNF-α and TGF-β were explored by using Western blot and ELISA.

RESULTS

We found that Cos promoted OGSCs proliferation in a dose-and time-dependent manner, accompanied by IL-2, TNF-α increase and IL-10, TGF-β decrease. Mouse monocyte-macrophages Leukemia cells(RAW) can also produce the same effect as Cos. When combined with Cos, it can enhance the proliferative effect of Cos in OGSCs, and further increase IL-2, TNF-α and further decrease IL-10, TGF-β. The macrophages can enhance the proliferative effect of Cos in OGSCs is also associated with the further increase in IL-2, TNF-α and the further decrease in IL-10, TGF-β. In this study, we determined that the anti-aging genes SIRT-1 and SIRT-3 protein levels were increased by Cos and RAW respectively, whereas the senescence-associated SA-β-Gal and aging genes P21 and P53 were decreased. Cos and RAW had a protective effect on OGSCs delaying aging. Furthermore, RAW can further decrease the SA-β-Gal and aging genes P21 and P53 by Cos, and further increase SIRT1 and SIRT3 protein levels in OGSCs by Cos.

CONCLUSION

In conclusion, Cos and macrophages have synergistic effects on improving OGSCs function and delaying ovarian aging by regulating inflammatory factors.

Sohlh1 loss of function male and female infertility model impacts overall health beyond gonadal dysfunction in mice†

Reproductive longevity is associated with health outcomes. Early menopause, loss of ovarian function, and male infertility are linked to shorter lifespan and increased adverse health outcomes. Here we examined the extragonadal effects of whole animal loss of spermatogenesis and oogenesis specific basic helix-loop-helix 1 (Sohlh1) gene in mice, a well-described mouse model of female and male infertility. Sohlh1 encodes a transcription factor that is primarily expressed in the male and female germline and regulates germline differentiation. The Sohlh1 knockout mouse model, just like human individuals with SOHLH1 loss of function, presents with hypergonadotropic hypogonadism and loss of ovarian function in females and impaired spermatogenesis in males, with a seemingly gonad restricted phenotype in both sexes. However, extragonadal phenotyping revealed that Sohlh1 deficiency leads to abnormal immune profiles in the blood and ovarian tissues of female animals, sex-specific alterations of metabolites, and behavior and cognition changes. Altogether, these results show that Sohlh1 deficiency impacts overall health in both male and female mice.

Cysteine-rich 61(CYR61) alleviates cyclophosphamide-induced proliferation inhibition in ovarian granulosa cells via suppressing NLRP3/caspase1-mediated pyroptosis

BACKGROUND

We investigated the level of Cysteine-rich 61 (CYR61) in premature ovarian failure as well as its regulatory molecular mechanism in this study.

METHODS AND RESULTS

Cyclophosphamide (CTX) was used to induce OGCs (rat ovarian granulosa cells) and rats to establish in vivo and in vitro premature ovarian failure models. H&E staining was used to detect the pathological changes of ovarian histopathology. Si-NLRP3 (NOD-like receptor thermal protein domain associated protein 3, NLRP3) and si-CYR61 were transfected into OGCs using lipofectamine 3000. RT-qPCR and western blot were used to detect the expressions of CYR61 in ovarian tissue and OGCs. It showed that the expression of CYR61 was significantly down-regulated in premature ovarian failure model. Cell viability was detected using a Cell Counting Kit-8 (CCK-8) kit. TUNEL (Terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling) staining was used to detect the apoptosis. 5-Ethynyl-2'-deoxyuridine (EdU) and SA-β-gal (senescence-associated β-galactosidase) staining were used to assess the proliferation and senescence. The expression of CYR61 in OGCs and ovarian tissues were detected by immunofluorescence and immunohistochemical staining. Overexpression of CYR61 significantly promoted OGCs proliferation and inhibited pyroptosis and apoptosis. Western blot was used to detect the protein expressions of p53 and p21 in OGCs. Flow cytometry was used to detect the pyroptosis. CYR61 overexpression inhibited the expression of NLRP3 and caspase-1 in CTX-induced OGCs according to western blot results. Moreover, we found that CYR61 overexpression down-regulated the protein expressions of p53 and p21 in CTX-induced OGCs.

CONCLUSION

CYR61 inhibited CTX-induced OGCs senescence, and the mechanism may be related to the regulation of caspase-1/NLRP3-induced pyroptosis.

Female germline stem cells: aging and anti-aging

The delay of ovarian aging and the fertility preservation of cancer patients are the eternal themes in the field of reproductive medicine. Acting as the pacemaker of female physiological aging, ovary is also considered as the principle player of cancer, cardiovascular diseases, cerebrovascular diseases, neurodegenerative diseases and etc. However, its aging mechanism and preventive measures are still unclear. Some researchers attempt to activate endogenous ovarian female germline stem cells (FGSCs) to restore ovarian function, as the most promising approach. FGSCs are stem cells in the adult ovaries that can be infinitely self-renewing and have the potential of committed differention. This review aims to elucidate FGSCs aging mechanism from multiple perspectives such as niches, immune disorder, chronic inflammation and oxidative stress. Therefore, the rebuilding nichs of FGSCs, regulation of immune dysfunction, anti-inflammation and oxidative stress remission are expected to restore or replenish FGSCs, ultimately to delay ovarian aging.

Umbilical Cord Mesenchymal Stem Cells Ameliorate Premature Ovarian Insufficiency in Rats

Premature ovarian insufficiency (POI) or premature ovarian failure (POF) is known as a state of hypergonadotropic hypogonadism. Stem cell therapy is expected to be used in the treatment of POI. The aim of the present study was to explore the feasibility and effectiveness of umbilical cord mesenchymal stem cell (UCMSC) transplantation for the treatment of POI in a rat model of POI induced by cyclophosphamide (CTX) injection. The ovarian function was examined by evaluating the weight of the ovary and body, estrus cycle, ovarian morphology, hormonal secretion, granulosa cell apoptosis, and fertility. The results showed that the ovarian function indicators of the modeled rats were comparable to those of the control rats after UCMSC transplantation, indicating that the ovarian function of the modeled rats recovered to a satisfactory extent. Our research may provide an experimental clue for the clinical application of UCMSC transplantation in the treatment of POI. Further experiments will focus on the detailed signaling pathway study of the molecular mechanisms of injury and repairment on the treatment with UCMSCs transplantation in the rat POI models.

The Role of T Cells in Ovarian Physiology and Infertility

Infertility affects one in six couples worldwide, with more than 48 million couples affected internationally. The prevalence of infertility is increasing which is thought to be attributed to delayed child-bearing due to socioeconomic factors. Since women are more prone to autoimmune diseases, we sought to describe the correlation between ovarian-mediated infertility and autoimmunity, and more specifically, the role of T cells in infertility. T cells prevent autoimmune diseases and allow maternal immune tolerance of the semi-allogeneic fetus during pregnancy. However, the role of T cells in ovarian physiology has yet to be fully understood.

Systematic Understanding of Anti-Aging Effect of Coenzyme Q10 on Oocyte Through a Network Pharmacology Approach

BACKGROUND

Maternal oocyte aging is strongly contributing to age-related decline in female fertility. Coenzyme Q10 (CoQ10) exerts positive effects in improving aging-related deterioration of oocyte quality, but the exact mechanism is unclear.

OBJECTIVE

To reveal the system-level mechanism of CoQ10's anti-aging effect on oocytes based on network pharmacology.

METHODS

This study adopted a systems network pharmacology approach, including target identification, data integration, network and module construction, bioinformatics analysis, molecular docking, and molecular dynamics simulation.

RESULT

A total of 27 potential therapeutic targets were screened out. Seven hub targets (PPARA, CAT, MAPK14, SQSTM1, HMOX1, GRB2, and GSR) were identified. Functional and pathway enrichment analysis indicated that these 27 putative targets exerted therapeutic effects on oocyte aging by regulating signaling pathways (e.g., PPAR, TNF, apoptosis, necroptosisn, prolactin, and MAPK signaling pathway), and are involved oxidation-reduction process, mitochondrion, enzyme binding, reactive oxygen species metabolic process, ATP binding, among others. In addition, five densely linked functional modules revealed the potential mechanisms of CoQ10 in improving aging-related deterioration of oocyte quality are closely related to antioxidant, mitochondrial function enhancement, autophagy, anti-apoptosis, and immune and endocrine system regulation. The molecular docking study reveals that seven hub targets have a good binding affinity towards CoQ10, and molecular dynamics simulation confirms the stability of the interaction between the hub targets and the CoQ10 ligand.

CONCLUSION

This network pharmacology study revealed the multiple mechanisms involved in the anti-aging effect of CoQ10 on oocytes. The molecular docking and molecular dynamics simulation provide evidence that CoQ10 may act on these hub targets to fight against oocytes aging.

Research Progress on the Treatment of Premature Ovarian Failure Using Mesenchymal Stem Cells: A Literature Review

Premature ovarian failure (POF) has become one of the main causes of infertility in women of childbearing age and the incidence of POF is increasing year by year, seriously affecting the physical and mental health of patients and increasing the economic burden on families and society as a whole. The etiology and pathogenesis of POF are complex and not very clear at present. Currently, hormone replacement therapy is mainly used to improve the symptoms of low estrogen, but cannot fundamentally solve the fertility problem. In recent years, stem cell (SC) transplantation has become one of the research hotspots in the treatment of POF. The results from animal experiments bring hope for the recovery of ovarian function and fertility in patients with POF. In this article, we searched the published literature between 2000 and 2020 from the PubMed database (https://pubmed.ncbi.nlm.nih.gov), and summarized the preclinical research data and possible therapeutic mechanism of mesenchymal stem cells (MSCs) in the treatment of POF. Our aim is to provide useful information for understanding POF and reference for follow-up research and treatment of POF.

Combination of Estradiol with Leukemia Inhibitory Factor Stimulates Granulosa Cells Differentiation into Oocyte-Like Cells

Purpose: Previous studies have documented that cumulus granulosa cells (GCs) can trans-differentiation into different non-ovarian cells, showing their multipotentiality to repopulate the injured cells in ovarian tissue. The current experiment is aimed to assess the differentiation capacity of human cumulus GCs toward the oocyte-like phenotype in vitro.

Methods: GCs were isolated from healthy female volunteers subjected to in vitro fertilization or intra-cytoplasmic sperm injection (IVF-ICSI). The effect of different media supplemented with leukemia inhibitory factors (LIFs), 5 ng/mL estradiol, and 0.005 IU/mL follicle-stimulating hormone (FSH) were investigated to the differentiation of GCs toward oocyte-like phenotype via monitoring the expression of Oct3/4 and GATA-4 using flow cytometry analysis. The expression of genes such as FIGLA, NOBOX, and SYCP3 was measured by real-time polymerase chain reaction (PCR) assay. We also assess morphological adaptation by using bright-field microscopic imaging.

Results: Exposure of GCs to LIFs increased the number of cells expressing stemness factor Oct3/4 coincided with the suppression of GATA-4 after 7 days (P < 0.05). We found that the transcript level of all genes FIGLA, Nobox, and SYCP-3 decreased in cells after treatment with a FSH (P < 0.05). According to our data, the incubation of GCs with estradiol increased the expression of genes related to the oocyte-like phenotype.

Conclusion: Our finding revealed that the combination of LIFs and estradiol could induce the GCs’ oogenesis capacity and thereby is possibly suggested as a therapeutic strategy during the occurrence of gynecological disorders.

Resumed ovarian function and pregnancy in early menopausal women by whole dimension subcortical ovarian administration of platelet-rich plasma and gonadotropins

OBJECTIVE

This study was designed to investigate if whole dimension subcortical ovarian administration of platelet-rich plasma with gonadotropin, in proximity to most ovarian follicles, is effective in restoring ovarian functions in women during early menopause.

METHODS

Platelet-rich plasma, prepared from 40 mL of autologous peripheral blood using the buffy coat method, was injected into extended subcortical area of bilateral ovaries along with recombinant follicle-stimulating hormone (rFSH) (Gonal-F 300IU) under laparoscopic guidance. The posttreatment ovarian folliculogenesis and serum levels of FSH, luteinizing hormone (LH), and estradiol were followed up for 6 months at weekly to monthly intervals. IVF was carried out in women resuming ovulatory functions.

RESULTS

Twelve early menopausal women with mean age of 44.42 ± 2.84 were enrolled. After treatment, 11 women resumed their menstrual period in 37.1 ± 23.5 days. Their average serum FSH was 70.47 ± 20.92 and 26.22 ± 17.55 IU/L, luteinizing hormone was 34.81 ± 11.86 and 14.3 ± 12.8 IU/L, before and after treatment, respectively. The mid-cycle E2 was 251.1 ± 143.8 pg/mL. Ten oocyte retrievals were carried out among six participants, four of them received controlled ovarian stimulation and another two using natural ovulation cycles. Thirteen mature eggs were retrieved which were then ICSI fertilized to obtain 10 normally fertilized 2PN oocytes. Two participants had cleavage stage embryos transferred of which one achieved clinical pregnancy.

CONCLUSIONS

Whole dimension subcortical ovarian administration of platelet-rich plasma with gonadotropin was shown to restore ovarian functions, at least temporarily, and could increase the probability of pregnancy using autologous oocytes in women with early menopause.

Mtor inhibition by INK128 extends functions of the ovary reconstituted from germline stem cells in aging and premature aging mice

Stem cell transplantation has been generally considered as promising therapeutics in preserving or recovering functions of lost, damaged, or aging tissues. Transplantation of primordial germ cells (PGCs) or oogonia stem cells (OSCs) can reconstitute ovarian functions that yet sustain for only short period of time, limiting potential application of stem cells in preservation of fertility and endocrine function. Here, we show that mTOR inhibition by INK128 extends the follicular and endocrine functions of the reconstituted ovaries in aging and premature aging mice following transplantation of PGCs/OSCs. Follicular development and endocrine functions of the reconstituted ovaries by transplanting PGCs into kidney capsule of the recipient mice were maintained by INK128 treatment for more than 12 weeks, in contrast to the controls for only about 4 weeks without receiving the mTOR inhibitors. Comparatively, rapamycin also can prolong the ovarian functions but for limited time. Furthermore, our data reveal that INK128 promotes mitochondrial function in addition to its known function in suppression of immune response and inflammation. Taken together, germline stem cell transplantation in combination with mTOR inhibition by INK128 improves and extends the reconstituted ovarian and endocrine functions in reproductive aging and premature aging mice.

The role of Chito-oligosaccharide in regulating ovarian germ stem cells function and restoring ovarian function in chemotherapy mice

In recent years, the discovery of ovarian germ stem cells (OGSCs) has provided a new research direction for the treatment of female infertility. The ovarian microenvironment affects the proliferation and differentiation of OGSCs, and immune cells and related cytokines are important components of the microenvironment. However, whether improving the ovarian microenvironment can regulate the proliferation of OGSCs and remodel ovarian function has not been reported. In this study, we chelated chito-oligosaccharide (COS) with fluorescein isothiocyanate (FITC) to track the distribution of COS in the body. COS was given to mice through the best route of administration, and the changes in ovarian and immune function were detected using assays of organ index, follicle counting, serum estrogen (E₂) and anti-Mullerian hormone (AMH) levels, and the expression of IL-2 and TNF-α in the ovaries. We found that COS significantly increased the organ index of the ovary and immune organs, reduced the rate of follicular atresia, increased the levels of E₂ and AMH hormones, and increased the protein expression of IL-2 and TNF-α in the ovary. Then, COS and OGSCs were co-cultured to observe the combination of COS and OGSCs, and measure the survival rate of OGSCs. With increasing time, the fluorescence intensity of cells gradually increased, and the cytokines IL-2 and TNF-α significantly promoted the proliferation of OGSCs. In conclusion, COS could significantly improve the ovarian and immune function of chemotherapy model mice, and improve the survival rate of OGSCs, which provided a preliminary blueprint for further exploring the mechanism of COS in protecting ovarian function.

Evaluation of safety, feasibility and efficacy of intra-ovarian transplantation of autologous adipose derived mesenchymal stromal cells in idiopathic premature ovarian failure patients: non-randomized clinical trial, phase I, first in human

Background

Premature ovarian failure (POF) is characterized by the loss of ovarian activity before the age of 40 years. Stem cell therapy has the capability to create a regenerative microenvironment and is a proposed treatment for POF-related infertility due to the presence of renewal folliculogenesis and germ cells in the adult ovaries. In this study, we assessed the safety, feasibility, efficacy and dose adjustment of autologous adipose-derived stromal cells (ADSCs) and their ability to improve ovarian function in POF patients.

Methods

This study was a non-randomized clinical trial, phase I. Nine women with a definitive diagnosis of POF were divided into three groups (n = 3 per group) that received either 5 × 10⁶, 10 × 10⁶, or 15 × 10⁶ autologous ADSCs suspension transplanted in the one ovary. Participants were followed-up at 24 h after the transplantation, and at 1 and 2 weeks, and 1, 2, 3, 6, and 12 months after the transplantation. The primary objective was to evaluate the safety of ADSCs transplantation. Secondary objectives included the effects of ADSCs transplantation on the resumption of menstruation, hormones level (Follicle-stimulating hormone (FSH) and anti-Müllerian hormone), ovarian function (Antral follicle count and ovary volume by ultrasonography evaluation) as well as dose escalation.

Results

Participants had not shown any early-onset possible side effects and secondary complications during follow-up. The menstruation resumption was observed in four patients which established for several months. In the 15 × 10⁶ group, two POF patients had a return of menstruation second months after the intervention. Two other POF patients in 5 × 10⁶ and 10 × 10⁶ cell groups reported menstruation resumption at 1 month after the intervention. We observed decreased serum FSH levels of less than 25 IU/l in four patients. In two patients in 5 × 10⁶ and 10 × 10⁶ cell groups, serum FSH showed an inconsistent decline during a 1 year follow up after ADSCs transplantation. The ovarian volume, AMH, and AFC were variable during the follow-up and no significant differences between cell groups (p > 0.05).

Conclusions

We showed the intra-ovarian embedding of ADSCs is safe and feasible and is associated with an inconsistent decline in serum FSH. This should be further investigated with a large RCT.

Trial registration

NCT02603744, Registered 13 November 2015 - Retrospectively registered, http://www.Clinicaltrials.gov

Protective roles and mechanisms of rosmarinic acid in cyclophosphamide-induced premature ovarian failure

The aim of this study was to investigate the protective effect of rosmarinic acid (RA) in a premature ovarian failure (POF) mouse model and the potential mechanisms. The POF model was induced by a single intraperitoneal injection of 120 mg/kg cyclophosphamide (CP). Additionally, 40 mg/kg RA was administered for 7 days before CP injection. The concentration of sex hormones was determined by fluorescence immunohistochemistry. Histological analysis was performed after ovarian tissue sections were stained with hematoxylin and eosin. The expression of the NLRP3 inflammasome was examined by western blot analysis and polymerase chain reaction. The expression of apoptosis markers of cytochrome c and caspase-3 was also detected by western blot analysis and immunohistochemistry. The results showed that RA not only decreased the ovarian index in POF mice but also improved the abnormal secretion of reproductive hormones associated with POF. Treatment with RA suppressed the ovarian expression of the NLRP3 inflammasome and regulated the ovarian expression of apoptosis-related proteins. The results suggested that RA exhibited a protective effect against CP-induced POF potentially by suppressing apoptosis and the NLRP3 inflammasome.

Identification of Key Genes and Potential New Biomarkers for Ovarian Aging: A Study Based on RNA-Sequencing Data

Ovarian aging leads to reproductive and endocrine dysfunction, causing the disorder of multiple organs in the body and even declined quality of offspring's health. However, few studies have investigated the changes in gene expression profile in the ovarian aging process. Here, we applied integrated bioinformatics to screen, identify, and validate the critical pathogenic genes involved in ovarian aging and uncover potential molecular mechanisms. The expression profiles of GSE84078 were downloaded from the Gene Expression Omnibus (GEO) database, which included the data from ovarian samples of 10 normal C57BL/6 mice, including old (21-22 months old, ovarian failure period) and young (5-6 months old, reproductive bloom period) ovaries. First, we filtered 931 differentially expressed genes (DEGs), including 876 upregulated and 55 downregulated genes through comparison between ovarian expression data from old and young mice. Functional enrichment analysis showed that biological functions of DEGs were primarily immune response regulation, cell-cell adhesion, and phagosome pathway. The most closely related genes among DEGs (Tyrobp, Rac2, Cd14, Zap70, Lcp2, Itgb2, H2-Ab1, and Fcer1g) were identified by constructing a protein-protein interaction (PPI) network and consequently verified using mRNA and protein quantitative detection. Finally, the immune cell infiltration in the ovarian aging process was also evaluated by applying CIBERSORT, and a correlation analysis between hub genes and immune cell type was also performed. The results suggested that plasma cells and naïve CD4+ T cells may participate in ovarian aging. The hub genes were positively correlated with memory B cells, plasma cells, M1 macrophages, Th17 cells, and immature dendritic cells. In conclusion, this study indicates that screening for DEGs and pathways in ovarian aging using bioinformatic analysis could provide potential clues for researchers to unveil the molecular mechanism underlying ovarian aging. These results could be of clinical significance and provide effective molecular targets for the treatment of ovarian aging.

Effects of Human Amnion-Derived Mesenchymal Stem Cell (hAD-MSC) Transplantation In Situ on Primary Ovarian Insufficiency in SD Rats

Human amnion-derived mesenchymal stem cell (hAD-MSC) transplantation can repair ovarian injury and improve ovarian function in rats with chemotherapy-induced primary ovarian insufficiency (POI). However, ensuring that stem cells home to the ovary to improve their effects on ovarian injury is challenging. This research aimed to directly inject ovarian tissue with hAD-MSCs and improve the homing of stem cells to the ovary. The animals were divided into POI, hAD-MSC (tail vein) treatment, hAD-MSC (in situ) treatment, and control groups. POI rat models were established by intraperitoneal injection of cyclophosphamide (CTX) and busulfan (BUS). The hAD-MSCs isolated from the amnion were injected into the tail vein or ovary of POI rats. The estrous cycle, serum sex hormone levels, follicle counts, ovarian pathological changes, and proteome of the ovaries were evaluated. hAD-MSCs were successfully isolated and cultured from the amnion. Both hAD-MSC (tail vein) and hAD-MSC (in situ) transplantation increased body weight, improved the AMH levels and follicle numbers, and reduced reproductive organ injuries in POI rats. Transplantation of hAD-MSCs (in situ) upregulated 24 proteins and downregulated 4 proteins. Both hAD-MSC (tail vein) and hAD-MSC (in situ) transplantations can repair ovarian injury and improve ovarian function in rats with chemotherapy-induced POI. The paracrine proteome of hAD-MSCs in the ovarian microenvironment can protect against chemotherapy-induced damage by reducing apoptosis and promoting angiogenesis, cell proliferation, and gene expression.

Resveratrol Plays a Protective Role against Premature Ovarian Failure and Prompts Female Germline Stem Cell Survival

This study was designed to investigate the protective effect of resveratrol (RES) on premature ovarian failure (POF) and the proliferation of female germline stem cells (FGSCs) at the tissue and cell levels. POF mice were lavaged with RES, and POF ovaries were co-cultured with RES and/or GANT61 in vitro. FGSCs were pretreated with Busulfan and RES and/or GANT61 and co-cultured with M1 macrophages, which were pretreated with RES. The weights of mice and their ovaries, as well as their follicle number, were measured. Ovarian function, antioxidative stress, inflammation, and FGSCs survival were evaluated. RES significantly increased the weights of POF mice and their ovaries as well as the number of follicles, while it decreased the atresia rate of follicles. Higher levels of Mvh, Oct4, SOD2, GPx, and CAT were detected after treatment with RES in vivo and in vitro. RES treatment resulted in significantly lower TNF-α and IL-6 concentrations and an obviously higher IL-10 concentration in the ovaries. In FGSCs, higher Mvh, Oct4, and SOD2 concentrations and lower TNF-α, IL-6, and MDA concentrations were measured in the RES group. Blockage of the Hh signaling pathway reversed the protective effect of RES on FGSCs. In conclusion, RES effectively improved the ovarian function of the POF model and the productive capacity of FGSCs via relieving oxidative stress and inflammation and a mechanism involving the Hh signaling pathway, suggesting that RES is a potential agent against POF and can aid in the survival of FGSCs.

The estrogen-macrophage interplay in the homeostasis of the female reproductive tract

BACKGROUND

Estrogens are known to orchestrate reproductive events and to regulate the immune system during infections and following tissue damage. Recent findings suggest that, in the absence of any danger signal, estrogens trigger the physiological expansion and functional specialization of macrophages, which are immune cells that populate the female reproductive tract (FRT) and are increasingly being recognized to participate in tissue homeostasis beyond their immune activity against infections. Although estrogens are the only female gonadal hormones that directly target macrophages, a comprehensive view of this endocrine-immune communication and its involvement in the FRT is still missing.

OBJECTIVE AND RATIONALE

Recent accomplishments encourage a revision of the literature on the ability of macrophages to respond to estrogens and induce tissue-specific functions required for reproductive events, with the aim to envision macrophages as key players in FRT homeostasis and mediators of the regenerative and trophic actions of estrogens.

SEARCH METHODS

We conducted a systematic search using PubMed and Ovid for human, animal (rodents) and cellular studies published until 2018 on estrogen action in macrophages and the activity of these cells in the FRT.

OUTCOMES

Our search identified the remarkable ability of macrophages to activate biochemical processes in response to estrogens in cell culture experiments. The distribution at specific locations, interaction with selected cells and acquisition of distinct phenotypes of macrophages in the FRT, as well as the cyclic renewal of these properties at each ovarian cycle, demonstrate the involvement of these cells in the homeostasis of reproductive events. Moreover, current evidence suggests an association between estrogen-macrophage signaling and the generation of a tolerant and regenerative environment in the FRT, although a causative link is still missing.

WIDER IMPLICATIONS

Dysregulation of the functions and estrogen responsiveness of FRT macrophages may be involved in infertility and estrogen- and macrophage-dependent gynecological diseases, such as ovarian cancer and endometriosis. Thus, more research is needed on the physiology and pharmacological control of this endocrine-immune interplay.

Mid-life fertility: Challenges & policy planning

This review highlights the challenges, priority areas of research and planning, strategies for regulation of services and the need to develop guidelines and laws for fertility treatments during mid-life. The success rate of all treatments is poor in advanced age women because of declining ovarian reserve and natural fertility. There is often a need of third-party involvement which has its own ethical, legal and medical issues. Welfare of children born to older women and early death of parents are important concerns. Most of the new techniques such as the pre-implantation genetic diagnosis, oocyte augmentation, use of stem cells or artificial gametes, ovarian tissue preservation and ovarian transplantation are directed to improve, preserve or replace the declining ovarian reserve. These techniques are costly and have limited availability, safety and efficacy data. Continued research and policies are required to keep pace with these techniques. The other important issues include the patients' personal autonomy and right of self-determination, welfare of offspring, public vs. private funding for research and development of new technologies vs. indiscriminate use of unproven technology. It is important that mid-life fertility is recognized as a distinct area of human reproduction requiring special considerations.

Research advances in the regulation of the putative ovarian germline stem cell niche on female germline stem cells

Stem cells are ideal seeding cells, which have the potential for self-renewal and multiple differentiation, and they play a fundamental role in maintaining homeostasis and regenerating and repairing tissue. The discovery of female germline stem cells (FGSCs) brings much hope for the postnatal renewal of oocytes and solving some female infertility problems. Ovarian function declines with increasing female age. Moreover, ovarian germline stem cell niche-aging could be the main cause of ovarian senescence, which ultimately leads to decreased follicle generation, declining female fertility, and age-related diseases, such as osteoporosis and ovarian cancer. The ovarian germline stem cell niche is the surrounding microenvironment in which FGSCs live, and it helps control the biological characteristics of FGSCs in many ways, such as nutritional supply and immunological cytokine secretion. This paper reviews the knowledge about the ovarian germline stem cell niche and its probable regulatory mechanisms on FGSCs, which provides valuable scientific information and scope for the prevention and treatment of ovarian senescence. Abbreviations: BMP: bone morphogenetic protein; Dpp: decapentaplegic; FGSC: female germline stem cell; IL, interleukin; OGSC: ovarian germline stem cells; ROS: reactive oxygen species; TGF, transforming growth factor; TNF, tumor necrosis factor.

Neonatal immune activation depletes the ovarian follicle reserve and alters ovarian acute inflammatory mediators in neonatal rats

Normal ovarian development is crucial for female reproductive success and longevity. Interruptions to the delicate process of initial folliculogenesis may lead to ovarian dysfunction. We have previously demonstrated that an early life immune challenge in the rat, induced by administration of lipopolysaccharide (LPS) on postnatal day (PND) 3 and 5, depletes ovarian follicle reserve long term. Here, we hypothesized that this neonatal immune challenge leads to an increase in peripheral and ovarian inflammatory signaling, contributing to an acute depletion of ovarian follicles. Morphological analysis of neonatal ovaries indicated that LPS administration significantly depleted PND 5 primordial follicle populations and accelerated follicle maturation. LPS exposure upregulated circulating interleukin 6, tumor necrosis factor alpha (TNFa), and C-reactive protein on PND 5, and upregulated ovarian mRNA expression of Tnfa, mitogen-activated protein kinase 8 (Mapk8/Jnk1), and growth differentiation factor 9 (Gdf9) (P < 0.05). Mass spectrometry and cell signaling pathway analysis indicated upregulation of cellular pathways associated with acute phase signaling, and cellular survival and assembly. Apoptosis assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling indicated significantly increased positive staining in the ovaries of LPS-treated neonates. These findings suggest that increased proinflammatory signaling within the neonatal ovary may be responsible for the LPS-induced depletion of the primordial follicle pool. These findings also have implications for female reproductive health, as the ovarian reserve is a major determinate of female reproductive longevity.

Effects of low-intensity pulsed ultrasound (LIPUS)-pretreated human amnion-derived mesenchymal stem cell (hAD-MSC) transplantation on primary ovarian insufficiency in rats

BACKGROUND

Human amnion-derived mesenchymal stem cells (hAD-MSCs) have the features of mesenchymal stem cells (MSCs). Low-intensity pulsed ultrasound (LIPUS) can promote the expression of various growth factors and anti-inflammatory molecules that are necessary to keep the follicle growing and to reduce granulosa cell (GC) apoptosis in the ovary. This study aims to explore the effects of LIPUS-pretreated hAD-MSC transplantation on chemotherapy-induced primary ovarian insufficiency (POI) in rats.

METHODS

The animals were divided into control, POI, hAD-MSC treatment, and LIPUS-pretreated hAD-MSC treatment groups. POI rat models were established by intraperitoneal injection of cyclophosphamide (CTX). The hAD-MSCs isolated from the amnion were exposed to LIPUS or sham irradiation for 5 consecutive days and injected into the tail vein of POI rats. Expression and secretion of growth factors promoted by LIPUS in hAD-MSCs were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) in vitro. Estrous cycle, serum sex hormone levels, follicle counts, ovarian pathological changes, GC apoptosis, Bcl2 and Bax expression, and pro-inflammatory cytokine levels in ovaries were examined.

RESULTS

Primary hAD-MSCs were successfully isolated from the amnion. LIPUS promoted the expression and secretion of growth factors in hAD-MSCs in vitro. Both hAD-MSC and LIPUS-pretreated hAD-MSC transplantation increased the body and reproductive organ weights, improved ovarian function, and reduced reproductive organ injuries in POI rats. Transplantation of hAD-MSCs increased the Bcl-2/Bax ratio and reduced GC apoptosis and ovarian inflammation induced by chemotherapy in ovaries. These effects could be improved by pretreatment with LIPUS on hAD-MSCs.

CONCLUSION

Both hAD-MSC transplantation and LIPUS-pretreated hAD-MSC transplantation can repair ovarian injury and improve ovarian function in rats with chemotherapy-induced POI. LIPUS-pretreated hAD-MSC transplantation is more advantageous for reducing inflammation, improving the local microenvironment, and inhibiting GC apoptosis induced by chemotherapy in ovarian tissue of POI rats.

Differentiation of Mouse Ovarian Stem Cells Toward Oocyte-Like Structure by Coculture with Granulosa Cells

An increasing body of evidence has confirmed existence and function of ovarian stem cells (OSCs). In this study, a novel approach on differentiation of OSCs into oocyte-like cells (OLCs) has been addressed. Recently, different methods have been recruited to isolate and describe aspects of OSCs, but newer and more convenient strategies in isolation are still growing. Herein, a morphology-based method was used to isolate OSCs. Cell suspension of mouse neonatal ovaries was cultured and formed colonies were harvested mechanically and cultivated on mouse embryonic fibroblasts. For differentiation induction, colonies transferred on inactive granulosa cells. Results showed that cells in colonies were positive for alkaline phosphatase activity and reverse transcription-polymerase chain reaction (RT-PCR) confirmed the pluripotency characteristics of cells. Immunofluorescence revealed a positive signal for OCT4, DAZL, MVH, and SSEA1 in colonies as well. Results of RT-PCR and immunofluorescence confirmed that some OLCs were generated within the germ stem cell (GSCs) colonies. The applicability of morphological selection for isolation of GSCs was verified. This method is easier and more economic than other techniques. Our results demonstrate that granulosa cells were effective in inducing the differentiation of OSCs into OLCs through direct cell-to-cell contacts.

Neo-oogenesis in mammals

Recently, the existence of a mechanism for neo-oogenesis in the ovaries of adult mammals has generated much controversy within reproductive biology. This mechanism, which proposes that the ovary has cells capable of renewing the follicular reserve, has been described for various species of mammals. The first evidence was found in prosimians and humans. However, these findings were not considered relevant because the predominant dogma for reproductive biology at the time was that of Zuckerman. This dogma states that female mammals are born with finite numbers of oocytes that decline throughout postnatal life. Currently, the concept of neo-oogenesis has gained momentum due to the discovery of cells with mitotic activity in adult ovaries of various mammalian species (mice, humans, rhesus monkeys, domestic animals such as pigs, and wild animals such as bats). Despite these reports, the concept of neo-oogenesis has not been widely accepted by the scientific community, generating much criticism and speculation about its accuracy because it has been impossible to reproduce some evidence. This controversy has led to the creation of two positions: one in favour of neo-oogenesis and the other against it. Various animal models have been used in support of both camps, including both classic laboratory animals and domestic and wild animals. The aim of this review is to critically present the current literature on the subject and to evaluate the arguments pro and contra neo-oogenesis in mammals.

Involvement of blood mononuclear cells in the infertility, age-associated diseases and cancer treatment

Blood mononuclear cells consist of T cells and monocyte derived cells. Beside immunity, the blood mononuclear cells belong to the complex tissue control system (TCS), where they exhibit morphostatic function by stimulating proliferation of tissue stem cells followed by cellular differentiation, that is stopped after attaining the proper functional stage, which differs among various tissue types. Therefore, the term immune and morphostatic system (IMS) should be implied. The TCS-mediated morphostasis also consists of vascular pericytes controlled by autonomic innervation, which is regulating the quantity of distinct tissues in vivo. Lack of proper differentiation of tissue cells by TCS causes either tissue underdevelopment, e.g., muscular dystrophy, or degenerative functional failures, e.g., type 1 diabetes and age-associated diseases. With the gradual IMS regression after 35 years of age the gonadal infertility develops, followed by a growing incidence of age-associated diseases and cancers. Without restoring an altered TCS function in a degenerative disease, the implantation of tissue-specific stem cells alone by regenerative medicine can not be successful. Transfused young blood could temporarily restore fertility to enable parenthood. The young blood could also temporarily alleviate aging diseases, and this can be extended by substances inducing IMS regeneration, like the honey bee propolis. The local and/or systemic use of honey bee propolis stopped hair and teeth loss, regressed varicose veins, improved altered hearing, and lowered high blood pressure and sugar levels. Complete regression of stage IV ovarian cancer with liver metastases after a simple elaborated immunotherapy is also reported.

The effect of the immune system on ovarian function and features of ovarian germline stem cells

In addition to its role in maintaining organism homeostasis, the immune system also plays a crucial role in the modulation of ovarian function, as it regulates ovarian development, follicular maturation, ovulation and the formation of the corpus luteum. Ovarian germline stem cells are pluripotent stem cells derived from the ovarian cortex that can differentiate into ovarian germ cells and primary granulosa cells. Recent work has demonstrated that the proliferation and differentiation of ovarian germline stem cells is regulated in part by immune cells and their secreted factors. This paper reviews the role of the immune system in the regulation of ovarian function, the relationship between immune components and ovarian germline stem cells and current research efforts in this field.

Novel Action of FSH on Stem Cells in Adult Mammalian Ovary Induces Postnatal Oogenesis and Primordial Follicle Assembly

Adult mammalian ovary has been under the scanner for more than a decade now since it was proposed to harbor stem cells that undergo postnatal oogenesis during reproductive period like spermatogenesis in testis. Stem cells are located in the ovary surface epithelium and exist in adult and menopausal ovary as well as in ovary with premature failure. Stem cells comprise two distinct populations including spherical, very small embryonic-like stem cells (VSELs which express nuclear OCT-4 and other pluripotent and primordial germ cells specific markers) and slightly bigger ovarian germ stem cells (OGSCs with cytoplasmic OCT-4 which are equivalent to spermatogonial stem cells in the testes). These stem cells have the ability to spontaneously differentiate into oocyte-like structures in vitro and on exposure to a younger healthy niche. Bone marrow may be an alternative source of these stem cells. The stem cells express FSHR and respond to FSH by undergoing self-renewal, clonal expansion, and initiating neo-oogenesis and primordial follicle assembly. VSELs are relatively quiescent and were recently reported to survive chemotherapy and initiate oogenesis in mice when exposed to FSH. This emerging understanding and further research in the field will help evolving novel strategies to manage ovarian pathologies and also towards oncofertility.

Novel methods of treating ovarian infertility in older and POF women, testicular infertility, and other human functional diseases

In vitro maturation (IVM) and in vitro fertilization (IVF) technologies are facing with growing demands of older women to conceive. Although ovarian stem cells (OSCs) of older women are capable of producing in vitro fresh oocyte-like cells (OLCs), such cells cannot respond to IVM and IVF due to the lack of granulosa cells required for their maturation. Follicular renewal is also dependent on support of circulating blood mononuclear cells. They induce intermediary stages of meiosis (metaphase I chromosomal duplication and crossover, anaphase, telophase, and cytokinesis) in newly emerging ovarian germ cells, as for the first time demonstrated here, induce formation of granulosa cells, and stimulate follicular growth and development. A pretreatment of OSC culture with mononuclear cells collected from blood of a young healthy fertile woman may cause differentiation of bipotential OSCs into both developing germ and granulosa cells. A small blood volume replacement may enable treatment of ovarian infertility in vivo. The transferred mononuclear cells may temporarily rejuvenate virtually all tissues, including improvement of the function of endocrine tissues. Formation of new follicles and their development may be sufficient for IVM and IVF. The novel proposed in vitro approaches may be used as a second possibility. Infertility of human males affects almost a half of the infertility cases worldwide. Small blood volume replacement from young healthy fertile men may also be easy approach for the improvement of sperm quality in older or other affected men. In addition, body rejuvenation by small blood volume replacement from young healthy individuals of the same sex could represent a decline of in vitro methodology in favor of in vivo treatment for human functional diseases. Here we propose for the first time that blood mononuclear cells are essential for rejuvenation of those tissues, where immune system components participate in an appropriate division and differentiation of tissue stem cells. If needed, small blood volume replacement from distinct young healthy individuals could be utilized in six month intervals for repair of young altered or aged reproductive and other tissue functions. Systemic and local use of honey bee propolis tincture is an alternative option for functional rejuvenation of some tissues.

Identification and characterization of epithelial cells derived from human ovarian follicular fluid

Introduction

Follicular fluid is important for follicular development and oocyte maturation. Evidence suggests that follicular fluid is not only rich in proteins but cells. Besides oocytes, the follicular fluid contains granulosa, thecal, and ovarian surface epithelial cells, and both granulosa and thecal cells are well-characterized. However, epithelial cells in follicular fluid are poorly studied. This study aims to isolate and characterize in vitro epithelial cells that originate from human ovarian follicular fluid retrieved in the assisted fertilization program.

Methods

Follicular fluid samples were collected from 20 women in the assisted reproduction program. Epithelial cells were characterized by flow cytometry assay, immunofluorescence staining, real-time PCR, and time lapse photography.

Results

Epithelial cell cultures were established from 18 samples. A small population of epithelial cells expresses germ-line stem cell markers, such as octamer-binding transcription factor 4 (OCT4), NANOG, and DEAD box polypeptide 4 (DDX4). In the epithelial cell culture system, oocyte-like cells formed spontaneously in vitro and expressed the following transcription markers: deleted in azoospermia-like (DAZL), developmental pluripotency associated protein 3 stella-related protein (STELLA), zona pellucida gene family C (ZPC), Syntaptonemal complex protein (SCP), and growth and differentiation factor 9 (GDF9). Some of the oocyte-like cells developed a zona pellucida-like structure. Both the symmetric and asymmetric division split of epithelial cells and early developing oocytes were observed using time lapse photography. Cell colonies were formed during epithelial culturing, which maintained and proliferated in an undifferentiated way on the feeder layer and expressed some pluripotency markers. These colonies differentiated in vitro into various somatic cell types in all three germ layers, but did not form teratoma when injected into immunodeficient mice. Furthermore, these epithelial cells could be differentiated directly to functional hepatocyte-like cells, which do not exist in ovarian tissues.

Conclusions

The epithelial cells derived from follicular fluid are a potential stem cell source with a pluripotent/multipotent character for safe application in oogenesis and regenerative medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0004-6) contains supplementary material, which is available to authorized users.

Stem cells, progenitor cells, and lineage decisions in the ovary

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic.

Isolation and characterization of stem cells in the adult mammalian ovary

Female mammals are born with a fixed pool of germ cells, which does not replenish during adult life. However, this has been recently challenged and adult ovaries produce oocytes throughout adult life just like sperm in the testes. Evidence is accumulating on the presence of ovarian stem cells, but the need for robust protocols to isolate, identify, further characterize, and subject them to various functionality tests is essential. Knowledge about the function and potential of ovarian stem cells is well demonstrated by various groups, but their true identity remains elusive because of the variability in the approaches used to identify them by different groups. In order to address this we have made attempts to compile our protocols to isolate, identify, characterize, and culture the stem cells using different animal models including human. Two distinct populations of stem cells exist in adult mammalian ovary, including very small embryonic-like stem cells (VSELs) and the progenitors termed ovarian germ stem cells (OGSCs). VSELs are relatively quiescent and undergo asymmetric cell division to give rise to OGSCs, which divide rapidly, occasionally form germ cell nests and undergo meiosis and differentiation into oocytes, which are surrounded by granulosa cells to assemble as primordial follicles.

Making gametes from pluripotent stem cells--a promising role for very small embryonic-like stem cells

The urge to have one's own biological child supersedes any desire in life. Several options have been used to obtain gametes including pluripotent stem cells (embryonic ES and induced pluripotent iPS stem cells); gonadal stem cells (spermatogonial SSCs, ovarian OSCs stem cells), bone marrow, mesenchymal cells and fetal skin. However, the field poses a huge challenge including inefficient existing protocols for differentiation, epigenetic and genetic changes associated with extensive in vitro manipulation and also ethical/regulatory constraints. A tremendous leap in the field occurred using mouse ES and iPS cells wherein they were first differentiated into epiblast-like cells and then primordial germ cell-like cells. These on further development produced sperm, oocytes and live offspring (had associated genetic problems). Evidently differentiating pluripotent stem cells into primordial germ cells (PGCs) remains a major bottleneck. Against this backdrop, we propose that a novel population of pluripotent stem cells termed very small embryonic-like stem cells (VSELs) may serve as an alternative, potential source of autologus gametes, keeping in mind that they are indeed PGCs surviving in adult mammalian ovaries and testes. Both VSELs and PGCs are pluripotent, relatively quiescent because of epigenetic modifications of parentally imprinted genes loci like Igf2-H19 and KCNQ1p57, share several markers like Stella, Fragilis, Mvh, Dppa2, Dppa4, Sall4, Blimp1 and functional receptors. VSELs are localized in the basement membrane of seminiferous tubules in testis and in the ovary surface epithelium. Ovarian stem cells from mouse, rabbit, sheep, marmoset and humans (menopausal women and those with premature ovarian failure) spontaneously differentiate into oocyte-like structures in vitro with no additional requirement of growth factors. Thus a more pragmatic option to obtain autologus gametes may be the pluripotent VSELs and if we could manipulate them in vivo - existing ethical and epigenetic/genetic concerns associated with in vitro culture may also be minimized. The field of oncofertility may undergo a sea-change and existing strategies of cryopreservation of gametes and gonadal tissue for fertility preservation in cancer patients will necessitate a revision. However, first the scientific community needs to arrive at a consensus about VSELs in the gonads and then work towards exploiting their potential.

Differential expression of pluripotent and germ cell markers in ovarian surface epithelium according to age in female mice

BACKGROUND

Many studies have proposed that putative ovarian stem cells (OSCs) derived from the ovarian surface epithelium (OSE) layer of adult mammalian ovaries can produce oocytes. Few studies have reported that ovaries of aged mammalian females including mice and women possess rare premeiotic germ cells that can generate oocytes. However, no studies have reported the changes of OSCs according to the age of the female. Therefore, this study evaluated pluripotent and germ cell marker expression in the intact ovary, scraped OSE, and postcultured OSE according to age in female mice.

METHODS

C57BL/6 female mice of 2 age groups (6-8 and 28-31 weeks) were superovulated by injection with 5 IU equine chorionic gonadotropin (eCG). Both ovaries were removed after 48 hours and scrapped to obtain OSE. Gene expressions of pluripotent (Oct-4, Sox-2, Nanog) and germ cell markers (c-Kit, GDF-9, and VASA) were evaluated by RT-PCR. VASA and GDF-9 were immune-localized in oocyte-like structures.

RESULTS

Expressions of germ cell markers in the intact ovary were significantly decreased in aged females, whereas expressions of pluripotent markers were not detected, regardless of age. Scraped OSE expression of all pluripotent and germ cell markers, except for c-Kit, was similar between both age groups. Three weeks postcultured OSE had significantly decreased expression of GDF-9 and VASA , but not c-Kit, in old mice, as compared to young mice; however there was no difference in the expression of other genes. The number of positively stained Oct-4 by immunohistochemistry in postcultured OSE was 2.5 times higher in young mice than aged mice. Oocyte-like structure was spontaneously produced in postcultured OSE. However, while that of young mice revealed a prominent nucleus, zona pellucida-like structure and cytoplasmic organelles, these features were not observed in old mice.

CONCLUSIONS

These results show that aged female mice have putative OSCs in OSE, but their differentiation potential, as well as the number of OSCs differs from those of young mice.

Ovarian adult stem cells: hope or pitfall?

For many years, ovarian biology has been based on the dogma that oocytes reserve in female mammals included a finite number, established before or at birth and it is determined by the number and quality of primordial follicles developed during the neonatal period. The restricted supply of oocytes in adult female mammals has been disputed in recent years by supporters of postnatal neo-oogenesis. Recent experimental data showed that ovarian surface epithelium and cortical tissue from both mouse and human were proved to contain very low proportion of cells able to propagate themselves, but also to generate immature oocytes in vitro or in vivo, when transplanted into immunodeficient mice ovaries. By mentioning several landmarks of ovarian stem cell reserve and addressing the exciting perspective of translation into clinical practice as treatment for infertility pathologies, the purpose of this article is to review the knowledge about adult mammalian ovarian stem cells, a topic that, since the first approach quickly attracted the attention of both the scientific media and patients.

Dynamics associated with spontaneous differentiation of ovarian stem cells in vitro

BACKGROUND

Recent studies suggest that ovarian germ line stem cells replenish oocyte-pool in adult stage, and challenge the central doctrine of 'fixed germ cell pool' in mammalian reproductive biology. Two distinct populations of spherical stem cells with high nucleo-cytoplasmic ratio have been recently identified in the adult mammalian ovary surface epithelium (OSE) including nuclear OCT-4A positive very small embryonic-like (VSELs) and cytoplasmic OCT-4 expressing ovarian germ stem cells (OGSCs). Three weeks culture of scraped OSE cells results in spontaneous differentiation of the stem cells into oocyte-like, parthenote-like, embryoid body-like structures and also embryonic stem cell-like colonies whereas epithelial cells attach and transform into a bed of mesenchymal cells. Present study was undertaken, to further characterize ovarian stem cells and to comprehend better the process of spontaneous differentiation of ovarian stem cells into oocyte-like structures in vitro.

METHODS

Ovarian stem cells were enriched by immunomagnetic sorting using SSEA-4 as a cell surface marker and were further characterized. Stem cells and clusters of OGSCs (reminiscent of germ cell nests in fetal ovaries), were characterized by immuno-localization for stem and germ cell specific markers and spontaneous differentiation in OSE cultures was studied by live cell imaging.

RESULTS

Differential expression of markers specific for pluripotent VSELs (nuclear OCT-4A, SSEA-4, CD133), OGSCs (cytoplasmic OCT-4) primordial germ cells (FRAGILIS, STELLA, VASA) and germ cells (DAZL, GDF-9, SCP-3) were studied. Within one week of culture, stem cells became bigger in size, developed abundant cytoplasm, differentiated into germ cells, revealed presence of Balbiani body-like structure (mitochondrial cloud) and exhibited characteristic cytoplasmic streaming.

CONCLUSIONS

Presence of germ cell nests, Balbiani body-like structures and cytoplasmic streaming extensively described during fetal ovary development, are indeed well recapitulated during in vitro oogenesis in adult OSE cultures along with characteristic expression of stem/germ cell/oocyte markers. Further studies are required to assess the genetic integrity of in vitro derived oocytes before harnessing their clinical potential. Advance in our knowledge about germ cell differentiation from stem cells will enable researchers to design better in vitro strategies which in turn may have relevance to reproductive biology and regenerative medicine.

Post-natal oogenesis: a concept for controversy that intensified during the last decade

For decades, scientists have considered that female mammals are born with a lifetime reserve of oocytes in the ovary, irrevocably fated to decline after birth. However, controversy in the matter of the possible presence of oocytes and granulosa cells that originate from stem cells in the adult mammalian ovaries has been expanded. The restricted supply of oocytes in adult female mammals has been disputed in recent years by supporters of neo-oogenesis, who claim that germline stem cells (GSCs) exist in the ovarian surface epithelium (OSE) or the bone marrow (BM). Differentiation of ovarian stem cells (OSCs) into oocytes, fibroblast-like cells, granulosa phenotype, neural and mesenchymal type cells and generation of germ cells from OSCs under the contribution of an OSC niche that consists of immune system-related cells and hormonal signalling has been claimed. Although these arguments have met with intense suspicion, their confirmation would necessitate the revision of the current classic knowledge of female reproductive biology.

Age-associated telomere shortening in mouse oocytes

BACKGROUND

Oocytes may undergo two types of aging. The first is induced by exposure to an aged ovarian microenvironment before being ovulated, known as 'reproductive or maternal aging', and the second by either a prolonged stay in the oviduct before fertilization or in vitro aging prior to insemination, known as 'postovulatory aging'. However, the molecular mechanisms underlying these aging processes remain to be elucidated. As telomere shortening in cultured somatic cells triggers replicative senescence, telomere shortening in oocytes during reproductive and postovulatory aging may predict developmental competence. This study aimed to ascertain the mechanisms underlying altered telomere biology in mouse oocytes during reproductive and postovulatory aging.

METHODS

We studied Tert expression patterns, telomerase activity, cytosolic reactive oxygen species (ROS) production, and telomere length in fresh oocytes from young versus reproductively-aged female mice retrieved from oviducts at 14 h post-human chorionic gonadotropin (hCG), in vivo or in vitro postovulatory-aged mouse oocytes at 23 h post-hCG. Oocytes were collected from super-ovulated C57BL/6 J mice of 6-8 weeks or 42-48 weeks of age. mRNA and protein expressions of the Tert gene were quantified using real-time quantitative reverse transcriptase polymerase chain reaction (Q-PCR) and immunochemistry. Telomerase activity was measured by a telomeric repeat amplification protocol assay, while telomere length was measured by Q-PCR and quantitative fluorescence in situ hybridization analyses.

RESULTS

The abundance of Tert expression in oocytes significantly decreased during reproductive and postovulatory aging. Immunofluorescent staining clearly demonstrated an altered pattern and intensity of TERT protein expression in oocytes during reproductive aging. Furthermore, relative telomerase activity (RTA) in oocytes from reproductively-aged females was significantly lower than that in oocytes from young females. In contrast, RTA in postovulatory-aged oocytes was similar to that in fresh oocytes. Oocytes from reproductively-aged females and postovulatory-aged oocytes showed higher ROS levels than oocytes from young females. Relative telomere length (RTL) was remarkably shorter in oocytes from reproductively-aged females compared to oocytes from young females. However, postovulatory aging had no significant effect on RTL of oocytes.

CONCLUSIONS

Long-term adverse effects of low telomerase activity and increased ROS exposure are likely associated with telomere shortening in oocytes from reproductively-aged female mice.

Plasticity of granulosa cells: on the crossroad of stemness and transdifferentiation potential

The ovarian follicle represents the basic functional unit of the ovary and consists of an oocyte, which is surrounded by granulosa cells (GCs). GCs play an important role in the growth and development of the follicle. They are subject to increased attention since it has recently been shown that the subpopulation of GCs within the growing follicle possesses exceptionally plasticity showing stem cell characteristics. In assisted reproduction programs, oocytes are retrieved from patients together with GCs, which are currently discarded daily, but could be an interesting subject to be researched and potentially used in regenerative medicine in the future. Isolated GCs expressed stem cell markers such as OCT-4, NANOG and SOX-2, showed high telomerase activity, and were in vitro differentiated into other cell types, otherwise not present within ovarian follicles. Recently another phenomenon demonstrated in GCs is transdifferentiation, which could explain many ovarian pathological conditions. Possible applications in regenerative medicine are also given.

Germline cells in ovarian surface epithelium of mammalians: a promising notion

It is a long held doctrine in reproductive biology that women are born with a finite number of oocytes and there is no oogenesis during the postnatal period. However, recent evidence challenges this by showing the presence of germ line stem cells in the human ovarian surface epithelium (OSE), which can serve as a source of germ cells, and differentiate into oocyte like structures. Postnatal renewal of oocytes may have enormous therapeutic potential especially in women facing the risk of premature ovarian failure idiopathically or iatrogenically after exposure to gonadotoxic chemotherapy and radiation for cancer therapy.This article reviews current knowledge on germ line stem cells in human OSE.